Hydraulically driven diaphragm pump

ABSTRACT

A diaphragm pump for pumping a fluid, such as paint, includes a diaphragm separating a first chamber for accommodating and dispensing the paint from a second chamber for accommodating a drive fluid, and a piston that reciprocates to drive the drive fluid within the second chamber in order to flex the diaphragm to provide the pumping action within the first chamber. The diaphragm pump also includes a backing ring mounted adjacent the diaphragm that is configured to distribute the drive fluid across the diaphragm to cause a flexible region of the diaphragm to flex toward the first chamber from the outer perimeter inward toward a central pumping surface in a rolling manner. This diaphragm movement results in substantially all of the paint adjacent the diaphragm within the first chamber to move out of the first chamber when the diaphragm reaches its travel limit, and thus improves the efficiency of the diaphragm pump. Additionally, the diaphragm pump includes a drive fluid inlet formed within the piston, such that reciprocating movement of the piston results in an inflow of drive fluid into the second chamber. An input port in the piston is continuously submerged in the drive fluid when open, thereby substantially eliminating the introduction of air into the drive fluid system and thus reducing drive fluid priming problems.

FIELD OF THE INVENTION

This invention relates to diaphragm pumps with increased efficiency dueto improvements in the diaphragm and drive fluid systems. Such diaphragmpumps typically have an oil section driving a load fluid section, topump paint for example.

BACKGROUND OF THE INVENTION

Diaphragm pumps for pumping paint and other fluids have been availablefor years for both industrial and commercial applications. Althoughthese pumps have been meeting consumer and professional requirements,changes in the market and economy, including increased marketcompetition and decreased profit margins, have increased the need formore cost effective production, cost reductions and improved pumpefficiencies. In addition, the expansion of the consumer market hasincreased the need for varying pump configurations at a range of pricelevels.

A drawback of the current pump that becomes evident when the pump isused in varying configurations, is a loss of prime. Pooling of hydraulicfluid away from the fluid inlet of the pump can occur in different pumporientations, especially when the fluid inlet is located at an outerlimit position within the pump. In these orientations, the hydraulicfluid portion of the pump takes in air or possibly runs dry causingnumerous mechanical problems that usually must be repaired by a servicerepresentative, thereby causing time delays, extra costs and loss ofproductivity.

In view of the deficiencies of currently available pumps and the everchanging needs of consumers, a need exists for a diaphragm pump thatdoesn't lose prime no matter what its orientation and has improvedefficiency without increasing manufacturing costs.

SUMMARY OF THE INVENTION

A diaphragm pump with improved efficiency and substantial elimination ofpriming problems at all orientations of the pump is provided in thepresent invention. The diaphragm pump includes a first chamber foraccommodating and dispensing a fluid to be pumped, such as paint, and asecond chamber for accommodating a drive fluid. A diaphragm separatesthe first chamber from the second chamber and has a first chamber sideand a second chamber side. The diaphragm includes an outer perimetermounting region, a thin inner perimeter flexible region, and a contouredcentral drive region having a stem on the second chamber side and acentral pumping surface on the first chamber side. The diaphragm ismovable from a first limit farthest away from the first chamber to asecond limit closest to the first chamber. A motor mounted eccentriccauses reciprocating movement of a piston located at least partiallywithin the second chamber. The piston movement results in correspondingdrive fluid movement within the second chamber, flexing the diaphragm toprovide a pumping action within the first chamber for dispensing thefluid to be pumped.

The diaphragm pump also includes a drive fluid inlet for supplying drivefluid to the second chamber. The drive fluid inlet has a drive fluidsupply passage formed axially within the piston having a first end and asecond end, the first end of the supply passage open to the secondchamber, and an input port formed within the piston transverse to thesupply passage. One end of the input port intersects the supply passagenear the second end of the supply passage, and the other end of theinput port is at least partially open to a drive fluid supply at apredetermined position of the piston within the second chamber. As thepiston reciprocates, the input port is closed to the drive fluid in thedrive fluid supply during a portion of the reciprocating movement of thepiston and the input port is open to the drive fluid in the drive fluidsupply at another portion of the reciprocating movement of the piston.This results in an inflow of drive fluid through the input port into thesupply passage and second chamber. When the input port is open it iscontinuously submerged in the drive fluid at all orientations of thepump, thereby substantially eliminating the introduction of air into thedrive fluid system, and thus reducing priming problems in the drivefluid section.

The diaphragm pump of the present invention also includes a backing ringmounted within the second chamber adjacent to the diaphragm defining acentral opening through which the stem of central drive region of thediaphragm passes. The backing ring has a plurality of holes configuredto distribute the drive fluid across the diaphragm after the drive fluidis driven by the drive fluid movement within the second chamber throughthe plurality of holes. It also has a diaphragm mating surface contouredto mate with the second chamber side of the diaphragm As the drive fluidpasses through the plurality of holes into a drive fluid volume definedbetween the diaphragm mating surface of the backing ring and the secondchamber side of the diaphragm, it forces the diaphragm membrane from thefirst limit toward the first chamber while flexing the flexible regionof the diaphragm toward the first chamber from the outer perimeterinward toward the central pumping surface in a rolling manner. Throughthis action, the diaphragm moves substantially all of the fluid to bepumped adjacent the diaphragm within the first chamber inward toward thecentral pumping surface and then out of the first chamber when thediaphragm reaches the second limit. Therefore, the efficiency of thediaphragm pump increases as more fluid is pumped with every stroke ofthe piston.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an end elevation view of a diaphragm pump in accordance withthe present invention with a cut-away view of the interior portion ofthe pump.

FIG. 2 is a side elevation view with a cut-away portion of the pump inFIG. 1 showing a close-up detail view of the piston and drive fluidinlet in bottom dead center position.

FIG. 3 is a side elevation view with a cut-away portion of the pumpsimilar to FIG. 2 except showing a close-up detail view of the pistonand drive fluid inlet in top dead center position.

FIG. 4 is a cross-sectional side view of a hydraulic housing portion ofthe pump useful in the practice of the present invention.

FIG. 5 is a partial cross-sectional end view of the hydraulic housing ofFIG. 4.

FIG. 6 is an oscillograph recording showing pressure at a paint spraygun verses time for a diaphragm pump having a drive fluid inlet openingheight of 0.035 inch.

FIG. 7A is an oscillograph recording showing pressure at a paint spraygun verses time for a diaphragm pump having a drive fluid inlet openingheight of 0.025 inch.

FIG. 7B is an oscillograph recording showing pressure at a paint spraygun verses time for a diaphragm pump having a drive fluid inlet openingheight of 0.045 inch.

FIG. 8 is a plot showing a family of curves of flow rate of the pumpedfluid versus pressure, at the spray gun, for a pump having differentsize drive fluid openings as a parameter.

FIG. 9 is an enlarged side elevation cross-sectional view of thediaphragm portion of the pump in FIG. 1.

FIG. 10 is plan view of a diaphragm backing ring in accordance with thepresent invention shown from the side opposite the diaphragm.

FIG. 11 is a cross-sectional view of the backing ring of FIG. 10 takenalong Line A—A.

FIG. 12 is a simplified cross-sectional representation of the diaphragmof FIG. 9 shown in its bottom-dead-center position.

FIG. 13 is a view similar to that of FIG. 12 except shown at a firsttime step as the diaphragm moves from bottom-dead-center totop-dead-center position.

FIG. 14 is a view similar to that of FIG. 12 except shown at a secondtime step as the diaphragm moves from bottom-dead-center totop-dead-center position.

FIG. 15 is a view similar to that of FIG. 12 except shown at a thirdtime step as the diaphragm moves from bottom-dead-center totop-dead-center position.

FIG. 16 is a simplified cross-sectional representation of the diaphragmof FIG. 9 shown in top-dead-center position.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the attached Figures, it is to be understood that likecomponents are labeled with like numerals throughout the severalFigures. FIG. 1 is a diaphragm pump 100 for pumping a fluid, such aspaint, stain or other suitable fluid, hereinafter referred to as“paint,” which preferably works together with a paint spray gun (notshown) connected to the pump 100 by a hose (also not shown) to paint asurface. The pump 100 includes a first chamber 150 for accommodating thepaint to be pumped, a second chamber 200 for holding a drive fluid 205,a motor 120 for powering the pump 100, and a frame 130 for supportingthe pump 100 and motor 120. A diaphragm 300 separates the first chamber150 from the second chamber 200 and conveys pumping action from thedrive fluid 205 to the paint.

Referring now also to FIGS. 2-4, the second chamber 200 includes ahousing 210 within which a reservoir 212 for holding the drive fluid205, a cylinder 214, and a drive fluid outlet 220 are formed. As shownbest in FIG. 4, the cylinder 214 includes three bore portions: a pistonportion 215, a diaphragm portion 216 and a backing ring bore 217.Referring now to FIGS. 1-3, the piston portion 215 houses a piston 230and the diaphragm portion 216 houses part of the diaphragm 300. As themotor 120 rotates a shaft 122, an eccentric 123 attached to the shaft122 at key 124 revolves within a bearing 126, causing the piston 230 toreciprocate within the cylinder 214. A piston spring 240, interposedbetween the housing 210 and a spring retainer 242 coupled to the piston230 by a retainer ring 244, provides a spring force to aid in the returnstroke of the piston 230.

Reciprocation of the piston 230 within cylinder 214 results in the drivefluid 205 passing into the piston portion 215 and then diaphragm portion216 of the cylinder 214. Within the diaphragm portion 216, the drivefluid 205 contacts the diaphragm 300 causing a reciprocating movement ofthe diaphragm 300 corresponding to the reciprocating movement of thepiston 230.

The first chamber 150 of the pump 100 includes a housing 152 thatattaches to the second chamber housing 210, sealed by the diaphragm 300.Paint enters the first chamber housing 152 at a paint inlet 110 thatcontains a check valve 155. The paint inlet 10 may be threaded tofacilitate connection to a supply hose or pipe (not shown) connectingthe pump to a supply of paint. The paint passes through a paint passage154 to encounter a pumping surface 314 located on the paint side of thediaphragm 300. The reciprocating movement of the diaphragm 300 thencauses the paint to flow out of the first chamber 150 under pressurethrough paint outlet 112 that also contains a check valve (not shown),and then through a hose to a paint spray gun (as described above).

Referring now most particularly to FIG. 1, pressure regulation of thepaint output occurs through adjustment of the drive fluid outlet 220.The drive fluid outlet 220 is fluidly connected to the diaphragm portion216 of the cylinder 214 and is fluidly coupled to a passage 225. Asshown in FIG. 4, a drive fluid return 221 (shown in dashed lines)fluidly connects passage 225 (also shown in dashed line) to a drivefluid return tube 223 that returns the drive fluid 205 to the reservoir212. Referring again to FIG. 1, a needle valve 222 located within bothdrive fluid passage 225 and drive fluid outlet 220 regulates the flow ofdrive fluid 205 from the cylinder 214 back to the reservoir 212.Adjustment of the pressure of the drive fluid 205 within the cylinder214, by adjustment of needle valve 222 through rotation of an externalpressure control knob 224, allows a user to regulate the output pressureof the paint being pumped.

As shown in FIGS. 1-3, also included on the pump 100 are an externalknob 114 for switching between “spray” and “prime” modes of the pump100, and a pusher valve 140. The spray knob 114 switches an internalvalve (not shown) directing paint to be returned to the paint source(for priming operation) and selectively to the outlet 112 (for painting,once the paint section is primed). The pusher valve 140 provides abackup feature for the outlet valve in paint outlet 112 by pushing theball portion of the outlet valve in the event of the ball becomingstuck.

Referring now to FIGS. 2, 3 and 5, as described above, flow of the drivefluid 205 into the cylinder 214 provides the driving force for thediaphragm 300 and, thus the paint out of the pump 100, and therefore isimportant to the overall function, performance and efficiency of thepump 100. In FIG. 5, a portion of a prior art pump 400 having a housing404 and a reservoir 405 is shown. Formed within the housing 404 is acylinder 410, similar to that shown in FIGS. 2 and 3, that has a pistonportion bore 412 and a diaphragm portion bore 414, in which a piston 416(shown in phantom) reciprocates, as described above. In pump 400, drivefluid flow into the cylinder 410 occurs through a drive fluid inlet 420that intersects the piston portion bore 412 near the transition to thediaphragm portion bore 414 of the cylinder 410.

The drive fluid inlet 420 includes an inlet opening 422 in fluidconnection with the piston portion bore 412, an inlet passage 424drilled through the housing 404 from the exterior to the inlet opening422, preferably perpendicular to the cylinder 410, and an intersectingpassage 428 formed parallel to the cylinder 410 fluidly connecting thereservoir 405 to the inlet passage 424. The exterior portion of theinlet passage 424 beyond the intersecting passage 428 is sealed by aplug 426, creating a single fluid pathway from the reservoir 405 to thepiston portion bore 412. Drive fluid enters this pathway through abubble filter 436 connected at elbow 434 to tube 432, which is fluidlycoupled to intersecting passage 428 by way of a tube coupler 430.

As the piston 416 reciprocates it repeatedly opens and closes the inletopening 422, thereby drawing drive fluid into the piston portion 412from the drive fluid inlet 420. Although functional, this type of drivefluid system requires multiple parts and multiple machining steps, thusincreasing the overall cost of the pump 400. In addition, although thefilter 436 is usually immersed within the drive fluid located in thereservoir 405, changing the pump 400 orientation may cause the filter436 to take in air instead of only drive fluid. This situation may causea loss of prime in the drive fluid portion of the pump 400, resulting inpump failure and/or damage.

The present invention overcomes the drive fluid system shortcomings ofthe prior art pump 400 by innovatively relocating the drive fluid inlet232 to the piston 230 itself. In FIGS. 2 and 3, the pump 100 of thepresent invention is shown wherein the piston 230 includes a drive fluidinput port 236 in fluid connection between the reservoir 212 and asupply passage 234. The supply passage 234 is preferably formed along alongitudinal axis of the piston 230 between the input port 236 and apiston end 231 on the diaphragm side of the piston 230, thus creating afluid pathway between the reservoir 212 and the piston portion 215. Aspositioned, the input port 236 remains continuously submerged within thedrive fluid 205 of the reservoir 212 at any orientation of the pump 100.Therefore, air entrapment in the drive fluid pathway is avoided, thusreducing drive fluid priming problems and repairs with the pump 100.

In FIG. 2, the piston 230 is shown in its most extended position,hereinafter the bottom-dead-center position. It is to be understood,however, that direction of travel of the piston 230 relative to theground is not implied by this designation, since the pump 100 may bepositioned in various orientations and thus the piston 230 may travel invarious directions relative to the ground. At bottom-dead-center, theinput port 236 preferably extends partially beyond the cylinder 214 atcylinder limit 213, providing a circular segment shaped opening havingan opening height 237. The input port 236 is preferably about0.1195±0.0015 inches in diameter, and the opening height 237 ispreferably about 0.035±0.010 inches, and more preferably within about±0.005 inches.

As shown in FIG. 3, as the piston 230 reciprocates it reaches its mostretracted position, hereinafter the top-dead-center position. It is tobe understood, however, that, as discussed above, no direction of travelrelative to the ground is to be implied from this designation. Attop-dead-center, the input port 236 is completely closed off from thereservoir 212 by the cylinder 214. With this configuration, the inputport 236 cooperates with the cylinder 230 to serve as a valve, therebycontrolling the flow of drive fluid 205 from the reservoir 212 into thecylinder 230.

The opening height 237 at bottom-dead-center, in combination with thediameter of the input port 236, provide a timing function reflected inthe time the pump 100 takes to reach a working pressure at the paintspray gun once the gun is opened. In FIG. 6, an oscillograph recordshows the pressure at the gun verses time for an opening height 237 of0.035 inches. Prior to the gun being opened, the stall pressure at thegun is about 2740 p.s.i. At about 15 seconds, the gun is opened and thepressure drops down to about an average of 2030 p.s.i. in about 1second. When the gun is again closed, at about 30.8 seconds, thepressure returns to its stall value in about 1.2 seconds. These testresults demonstrate an almost flat, extremely quick recovery time of thepump at this opening height 237, making it an optimum opening heightvalue.

By comparison, FIG. 7A shows the pressure verses time results of a 0.025inch opening height, wherein the recovery time is upwards of about 6.5seconds to reach the working pressure at the gun. FIG. 7B shows thepressure verses time results of a 0.045 inch opening, wherein recoverytime is also upwards of about 6.5 seconds. The recovery times (notshown) for both a 0.015 and a 0.065 inch opening heights are both in therange of about 10-11 seconds. As is apparent from this data, as theopening height 237 varies from an optimum value of 0.035 inches, therecovery times becoming larger, making the pump performance lessefficient.

In addition, as shown in FIG. 8, the opening height 237 of about 0.035inches provides a good flow rate, in the range of about 0.27 to 0.28gallons per minute, at a working gun pressure range of 2000 to 2500p.s.i., which is the preferred range for latex paint to shear andatomize at the tip of the paint spray gun. The other opening heightvalues, also shown in FIG. 8, provide varying flow rates at this workingpressure range. The flow rates of the larger opening height values dropoff significantly in this pressure range indicating their inefficiencyand, thus, unsuitability for use in this pressure range. In contrast,the smaller openings demonstrate higher flow rates and, thus, betterperformance in this pressure range. However, when viewed in combinationwith the recovery time results of these smaller openings, it can be seenthat they are less suitable than the preferable opening of 0.035 inchesbecause the end user will cause repetitive opening and closing of thespray gun as the user coats a surface with the paint and, thus, will bemore aware of the smaller opening's deficiencies in recovery time thanof the possible higher performance at a full-open condition.

The ability of the pump 100 of the present invention to function at theabove described preferred parameters is facilitated by an improvedability to machine the input port 236 with precision. The piston 230 ispreferably formed from stainless steel, allowing precise machining ofthe drive fluid inlet 232. In FIG. 5, the prior art inlet opening 422has the same general diameter as the input port 236, however theresulting opening height 423 can vary from about 0.020 to 0.060 inches.This variation is due to tolerance build-up in machining of the inletopening 422 through the housing 404. In contrast, the input port 236 ofthe present invention may be precisely drilled in the piston 230, andthus is not susceptible to tolerance build-up errors of the samemagnitude. Therefore, the overall performance of the pump 100 is animprovement over that of the prior art pump 400. In addition, the amountof machining necessary is reduced in the present invention pump 100,requiring two precision holes 234, 236 drilled within the piston 230verses the three bores of the prior art 422, 424, 428, plus sealing ofthe exterior portion of the drive fluid inlet with plug 426.

Another improvement of the present invention over the prior art is thereduction in parts needed to perform the drive fluid input function. Asshown in FIG. 5, the tube coupler 430, tube 432, elbow coupler 434 andbubble filter 436 are all required as part of the drive fluid inletsystem. In contrast, the present invention requires no additional parts,but instead makes use of the already provided piston 230 to perform thesame function.

Referring now to FIGS. 2 and 9, as described above, once the drive fluid205 enters the piston portion 215 it acts on the diaphragm 300 inresponse to the reciprocating action of the piston 230. As shown in FIG.9, the diaphragm 300 includes a central drive region 306 having a stem308 that extends into the diaphragm portion 216 of the cylinder 214.This central region 306 thins into a membrane toward an outer perimeterforming a flexible region 304 that extends further outward to form amounting region 302 around the outer perimeter of the diaphragm 300. Themounting region 302 is sandwiched between the first chamber housing 152and the second chamber housing 210 to seal the drive fluid side from thepaint pumping side of the pump 100, and to hold the diaphragm 300 inposition. To facilitate an adequate seal between the two chambers 150,200, both the first chamber housing 152 and the second chamber housing210 include a series of knurled rings 153, 211, respectively, formedwithin the housings 152, 210 to grip the mounting region 302 of thediaphragm 300. Also preferably included, but not shown, are a number ofmounting holes, formed as four symmetrically placed tabs around theouter perimeter of the mounting region 302 having through holes throughwhich four mounting screws (not shown) pass when the first chamber 150is coupled to the second chamber 200.

Positioned within the backing ring bore 217 is a backing ring 320 thatincludes an opening 328 through which the stem 308 passes, and a matingsurface 322 contoured to correspond to the stem-side configuration ofthe diaphragm's central region 306, hereinafter the drive surface 307.Referring now also to FIGS. 10 and 11, the backing ring 320 includes aseries of through holes 324 symmetrically located in two concentric ringpatterns around the opening 328.

Also preferably included in the backing ring 320 is a bore 327 with aradiused inside corner 329, formed in a base 323 on the piston-side ofthe backing ring 320. A spring 310 encircling the stem 308 is interposedbetween bore 327 and a nut 312 threaded onto the stem 308. The spring310 provides a spring force to aid in the return movement of thediaphragm 300 away from the first chamber 150.

Connecting the bore 327 to the holes 324 are a plurality of grooves 326that facilitate the passage of drive fluid 205 from the diaphragmportion 216 through the backing ring holes 324 and into contact with thedrive surface 307 of the diaphragm's central drive region 306. Thepressure of the drive fluid 205 causes the diaphragm 300 to move awayfirm the piston 230, toward the first chamber 150, deflecting at theflexing region 304.

Within the first chamber 150, a corresponding bore 156 is formedopposite the second chamber bore 217. Located within the first chamberbore 156 is a paint ring 160 having an opening 161 adjacent the paintpassage 154, and a diaphragm mating surface 162 contoured to correspondto the configuration of the diaphragm flexible region 304 when thediaphragm 300 moves toward the paint passage 154. A paint chamber 170located adjacent the paint passage 154 is defined by the diaphragmmating surface 162 of the paint ring 160 and the pumping surface 314 ofthe diaphragm 300. The paint chamber 170 includes a confined perimeterregion 171 located at the perimeter of the paint chamber 170 where thediaphragm flexible region 304 contacts the paint ring 160.

As stated above, the reciprocating motion of the piston 230 causes acorresponding reciprocating motion of the diaphragm 300. As the piston230 moves away from the diaphragm 300, the diaphragm is drawn towardsthe backing ring 320 with the help of the spring force caused by spring310, and paint is drawn in to the first chamber 150 through the paintinlet 110. As shown in FIGS. 2 and 3, the check valve 155 that ispositioned within the paint passage 154 allows paint inflow into thepaint chamber 170. When the piston 230 moves toward the diaphragm 300,the increase in pressure due to the inflow of drive fluid 205 causes thediaphragm 300 to move away from the backing ring 320, pushing the paintlocated within the paint chamber 170 out of the chamber 170. The checkvalve 155 closes against the pressure of the outflowing paint causingthe paint to divert through the paint outlet 112.

The efficiency of the pump 100, therefore, depends in a large part onthe diaphragm's ability to move the paint out of the paint chamber 170relative to its drive fluid driven motion. A shortcoming of prior artdiaphragm pumps is the formation of pockets of stagnant paint within thepaint chamber 170 in the perimeter region 171. Not only does the priorart pump's inability to push this volume of paint out of the pump witheach stroke of the piston result in inefficiency, but it also results inproblems related to the stagnant paint within the pump. The stagnantareas lodged between the diaphragm 300 and the paint chamber housing 152are difficult to adequately clear out during cleaning of the pump 100.However, if these stagnant areas are not adequately flushed, the paintwill eventually dry and the pump 100 will ultimately fail to function.

The diaphragm pump 100 of the present invention overcomes theseshortcomings through innovative modifications to the backing ring 320that result in expulsion of substantially all of the paint within thepaint chamber 170, thereby increasing the efficiency of the pump 100.Between the drive surface 307 and the mating surface 322 of the backingring 320, a drive fluid chamber 350 is defined that changes in shape andvolume as the diaphragm 300 reciprocates. The inflow of drive fluid 205into this chamber 350 through the series of holes 324 and thedistribution of the drive fluid 205 within the chamber 350 are bothbased on the mating surface 322 profile, which is thus a critical factorin the movement of the diaphragm 300 and the expulsion of paint from thepaint chamber 170. In addition, the mating surface 322 profile has a keyrole in the expulsion of drive fluid 205 from the chamber 350 when thediaphragm 300 moves toward the piston 230, thereby allowing for moreefficient use of the inflowing drive fluid 205 on the next stroke of thepiston 230.

As shown in FIG. 11, the diaphragm mating surface 322 of the backingring 320 is shaped by a depression 332 formed on the drive side 325 ofthe ringy 320. The depression 332 includes a shoulder 337 formed at anangle 341 relative to the base 323 of preferably about 3.64 degrees, anda wall 336 sloping down from the shoulder 337 to a floor 334. The angle340 of the wall 336 is preferably about 45 degrees. The overall diameter330 of the ring 320 is preferably about 1.334 inches and the overalldepth 331 of the ring 320 is preferably about 0.380 inches, being sizedto mate with the bore 217 and the diaphragm 300. The preferable radius343 of the depression 332 without the shoulder 337, as measured from alongitudinal centerline 321, is about 0.471 inches and the depth 335 ofthe depression 332 is preferably about 0.196 inches. A smooth transitionfrom the angled shoulder 337 to the angled wall 336 is preferablyachieved by a radiused corer 339 having a radius of about 0.138 inches.A smooth transition from the angled wall 336 to the floor 334 is alsopreferably provided by a radiused comtier 338 having a radius of about0.136 inches.

The opening 328 passes through the floor 334 of the depression 332, andthe series of holes 324, preferably each of about 0.079 inches indiameter, intersect the mating surface 322 of the depression 332 nearthe floor/wall transition and near the wall/shoulder transition atradiuses of about 0.295 and 0.512 inches from axis 321. When the drivefluid 205 is driven by the piston 230 stroke toward the diaphragm 300,the drive fluid encounters the backing ring bore 327 and is distributedout of the bore 327 through grooves 326 to the outer ring of holes 324,the inner ring of holes 324 and opening 328. The drive fluid 205 entersthe drive fluid chamber 350 at various points around the mating surface322, acting directly on the drive surface 307 of the diaphragm 300 anddistributing throughout the drive fluid chamber 350 to act on the drivesurface 307 at other locations. The pressure of the inflowing drivefluid 205 causes the diaphragm 300 to move toward the first chamber 150,thereby pushing the paint out of the adjacent paint chamber 170.

The backing ring 320 is preferably formed from Delrin™. The backing ring320 may be molded to exact specifications. However, other suitablematerials and fabrication methods are also contemplated and within thescope of the present invention.

In FIGS. 12-16, the movement of the diaphragm 300, from a first limit ina position closest to the piston 230, or bottom-dead-center position (inFIG. 12) to a second limit at a position farthest from the piston 230,or top-dead-center position (in FIG. 16), is illustrated as a series oftime steps, Steps 360, 362, 364, 366 and 368, respectively. In FIG. 12,on the outward stroke of the piston 230. the diaphragm 300 is drawnagainst the mating surface 322 of the backing ring 320 (Step 360),thereby minimizing the volume of the drive fluid chamber 350 and forcingthe drive fluid 205 back into the diaphragm portion 216 of the cylinder214. At this time, paint is drawn into the paint chamber 170 from thepaint source.

In FIG. 13, as the direction of the piston stroke changes and the drivefluid 205 inflows from the diaphragm portion 216, the diaphragm 300starts to move away from the piston 230 and toward the first chamber 150(Step 362), creating a partial volume in drive fluid chamber 350. Thepumping surface 314 of the diaphragm 300 pushes on the volume of paintwithin the paint chamber 170 forcing it out through the paint outlet112.

In FIG. 14, as the drive fluid 205 continues to inflow into the drivefluid chamber 350, the flexible region 304 of the diaphragm 300 startsto deflect toward the mating surface 162 of the paint ring 160 (shown inphantom) (Step 364) causing the paint located in the perimeter region171 of the paint chamber 170 to move toward the center of the pumpingsurface 314.

In FIG. 15, with the continuing inflow of drive fluid 205 into the drivefluid chamber 350, the flexible region 304 deflects enough to startconforming to the contour of the paint ring mating surface 162 from theperimeter inward toward the center (Step 366). The paint located in theperimeter region 171 of the paint chamber 170 is forced toward thecenter to be expelled out of the chamber 170 along with the centralvolume of paint within the chamber 170.

In FIG. 16, the diaphragm 300 has reached its top-dead-center position(Step 368). The volume of the drive fluid chamber 350 is at maximum, andthe volume of the paint chamber 170 is at its minimum. The flexibleregion 304 of the diaphragm 300 has deflected to substantially conformto the contour of the paint ring mating surface 162, thereby expellingsubstantially all of the paint within the perimeter region 171 of thepaint chamber 170. With substantially all of this paint expelled, noregions of stagnant paint remain within the perimeter region 171 of thepaint chamber 170, thereby fully utilizing the stroke of the pump 100 topump paint to the paint spray gun to be applied to a surface andeliminating the shortcomings of the prior art pump design. Although onlyone half of the reciprocating cycle of the diaphragm 300 has beenillustrated, it is to be understood that diaphragm 300 returns to theposition shown in FIG. 12 after reaching the position shown in FIG. 16,during which time a new volume of paint enters chamber 170.

Through the innovative redesign of the drive fluid inlet, the presentinvention pump eliminates pump problems due to air in the drive fluidsystem, decreases the number of parts needed to provide the same drivefluid function, and decreases the amount of machining involved inproducing the drive fluid system. as well as errors arising from suchmachining. Through the innovative improvements in the diaphragm backingring design, the present invention pump is able to fully utilize thedrive fluid provided to efficiently expel the paint from the pump.

Although the present invention has been described with reference topreferred embodiments, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the spiritand scope of the invention. In addition, the invention is not to betaken as limited to all of the details thereof as modifications andvariations thereof may be made without departing from the spirit orscope of the invention.

What is claimed is:
 1. A diaphragm pump apparatus comprising: a. a firstchamber that accommodates and dispenses a fluid to be pumped; b. asecond chamber that accommodates a drive fluid; c. a diaphragm thatseparates the first chamber from the second chamber and has a firstchamber side and a second chamber side, the diaphragm including an outerperimeter mounting region, a thin inner perimeter flexible region, and acurvedly contoured central drive region having a stem on the secondchamber side and a central pumping surface on the first chamber side,the diaphragm movable from a first limit farthest away from the firstchamber to a second limit closest to the first chamber; d. a pistonlocated at least partially within the second chamber driven by a motormounted eccentric that causes reciprocating movement of the piston, thepiston movement resulting in corresponding drive fluid movement withinthe second chamber; and e. a backing ring mounted within the secondchamber adjacent to the diaphragm defining a central opening throughwhich the stem of central drive region of the diaphragm passes, thebacking ring including: i) a plurality of holes passing through thebacking ring, the plurality of holes configured to distribute the drivefluid across the flexible region and the central drive region of thediaphragm after the drive fluid is driven by the drive fluid movementwithin the second chamber through the plurality of holes, at least someof the plurality of holes positioned within the backing ring oppositethe flexible region of the diaphragm; and ii) a diaphragm mating surfacecurvedly contoured to mate with the second chamber side of thediaphragm, such that pressure formed by the drive fluid passing throughthe plurality or holes into a drive fluid volume located between thediaphragm mating surface of the backing ring and the second chamber sideof the diaphragm drives the diaphragm from first the limit toward thefirst chamber while flexing the flexible region of the diaphragm towardthe first chamber from the outer perimeter inward toward the centralpumping surface in a rolling manner, the diaphragm moving substantiallyall of the fluid to be pumped adjacent the diaphragm within the firstchamber radially inward toward the central pumping surface and then outof the first chamber when the diaphragm reaches the second limit.
 2. Thediaphragm pump apparatus of claim 1, wherein the diaphragm matingsurface of the backing ring substantially conforms to the second chamberside of the diaphragm when the diaphragm is at the first limit.
 3. Thediaphragm pump apparatus of claim 2, wherein substantially all of thedrive fluid located in the drive fluid volume during reciprocatingmovement of the diaphragm from the first limit to the second limit isremoved from the drive fluid volume when the diaphragm reaches the firstlimit.
 4. The diaphragm pump apparatus of claim 3, wherein the secondchamber comprises a reservoir and a piston portion in fluidcommunication between the reservoir and the diaphragm.
 5. The diaphragmpump apparatus of claim 4, further comprising a drive fluid outlethaving a valve, the outlet in fluid communication between the pistonportion and the reservoir, wherein drive fluid removed from the drivefluid volume passes back into the reservoir through the drive fluidoutlet.
 6. The diaphragm pump apparatus of claim 1, wherein the firstchamber comprises a first chamber ring mounted within the first chamberadjacent the diaphragm, the first chamber ring inicluding a diaphragmmating surface contoured to mate with the first chamber side of thediaphragm to facilitate the movement of the fluid to be pumped towardthe central pumping surface.
 7. The diaphragm pump apparatus of claim 6,wherein the flexible region of the diaphragm conforms to the firstchamber ring diaphragm mating surface at the second limit of thediaphragm.
 8. The diaphragm pump apparatus of claim 1, wherein thediaphragm mating surface comprises an annular top surface formed arounda perimeter of the backing ring and a depression formed within a centralportion of the backing ring about a longitudinal axis passing throughthe center of the backing ring, the depression including a flooradjacent the central opening of the backing ring, and an angled wallformed between the depression floor and the top surface, with theplurality of holes positioned opposite the flexible region of thediaphragm intersecting the annular top surface of the backing ring. 9.The diaphragm pump apparatus of claim 8, wherein the top surface isformed at an angle relative to a plane that is perpendicular to thelongitudinal axis of the backing ring.
 10. The diaphragm pump apparatusof claim 9, wherein the angle of the top surface is about 3.6 degrees.11. The diaphragm pump apparatus of claim 8, wherein the angle of thedepression wall is about 45 degrees relative to the longitudinal axis ofthe backing ring.
 12. A diaphragm pump apparatus comprising: a. a firstchamber for accommodating and dispensing a fluid to be pumped; b. asecond chamber for accommodating a drive fluid, the second chamber influid communication with a drive fluid reservoir substantially filledwith a quantity of drive fluid; c. a diaphragm that separates the firstchamber from the second chamber and has a first chamber side and asecond chamber side, the diaphragm including an outer perimeter mountingregion, a thin inner perimeter flexible region, and a curvedly contouredcentral drive region having a stem on the second chamber side and acentral pumping surface on the first chamber side, the diaphragm movablefrom a first limit farthest away from the first chamber to a secondlimit closest to the first chamber; d. a piston having first and secondends with the first end located at least partially within a pistoncylinder having a wall and a passage included as part of the secondchamber, the piston being driven at the second end by a motor mountedeccentric causing reciprocating movement of the piston within the pistoncylinder, the piston movement resulting in corresponding drive fluidmovement within the second chamber flexing the diaphragm to provide apumping action within the first chamber for dispensing the fluid to bepumped; e. a drive fluid inlet for supplying drive fluid to the secondchamber from the drive fluid reservoir, the drive fluid inlet including:i) a drive fluid supply passage formed axially within the piston havinga first end and a second end, the first end of the supply passage opento the second chamber at the first end of the piston; and ii) an inputport formed within the piston transverse to the supply passage, an innerend of the input port intersecting the supply passage near the secondend of the supply passage, and an outer end of the input port open to anexterior of the piston, the input port positioned within an interior ofthe drive fluid reservoir with the outer end of the input port submergedin the drive fluid at a predetermined position of the piston within thepiston cylinder of the second chamber, such that the outer end of theinput port is closed by the piston cylinder to the drive fluid in thedrive fluid reservoir during a portion of the reciprocating movemnent ofthe piston, and at least a portion of the outer end of the input port isopen to and submerged in the drive fluid in the drive fluid reservoir atanother portion of the reciprocating movement of the piston resulting inan inflow of drive fluid through the input port into the supply passageand second chamber; and f. a backing ring mounted within the secondchamber adjacent to the diaphragm defining a central opening throughwhich the stem of central drive region of the diaphragm passes, thebacking ring comprising: i) a plurality of holes configured todistribute the drive fluid across the flexible region and the centraldrive region of the diaphragm after the drive fluid is driven by thedrive fluid movement within the second chamber through the plurality ofholes, at least some of the plurality of holes positioned within thebacking ring opposite the flexible region of the diaphragm; and ii) adiaphragm mating surface curvedly contoured to mate with the secondchamber side of the diaphragm, such that pressure formed by the drivefluid passing through the plurality of holes into a drive fluid volumedefined between the diaphragm mating surface of the backing ring and thesecond chamber side of the diaphragm drives the diaphragm from the firstlimit toward the first chamber while flexing the flexible region of thediaphragm toward the first chamber from the outer perimeter inwardtoward the central pumping surface in a rolling manner, the diaphragmmoving substantially all of the fluid to be pumped adjacent thediaphragm within the first chamber inward toward the central pumpingsurface and then out of the first chamber when the diaphragm reaches thesecond limit.
 13. A method of pumping a fluid using a diaphragm pumpapparatus comprising a first chamber that accommodates and dispenses afluid to be pumped, a second chamber that accommodates a drive fluid,and a diaphragm that separates the first chamber from the secondchamber, the method comprising the steps of: a. providing a drive fluidwithin the second chamber from a drive fluid reservoir; b. providing afluid to be pumped within the first chamber; c. flexing a flexibleregion of the diaphragm from an outer perimeter inward in a rollingmanner so that the flexible region of the diaphragm conforms to acontoured portion of the first chamber to push substantially all thefluid to be pumped adjacent to a first chamber side of the diaphragmradially inward and then out of the first chamber, flexing of theflexible region occurring by the delivery of the drive fluid to thesecond chamber, without air introduction into the second chamber, via adrive fluid supply passage formed within a piston and open to the secondchamber, the piston having an input port fluidly coupled to the supplypassage and positioned within the interior of the drive fluid reservoirso as to submerge the input portion within the drive fluid in the drivefluid reservoir at a predetermined position of the piston within thesecond chamber, the piston closing the input port to the drive fluid inthe drive fluid reservoir during a portion of a reciprocating movementof the piston and submerging the input port into the drive fluid in thedrive fluid reservoir at another portion of the reciprocating movementof the piston resulting in controlled inflow of drive fluid through theinput port into the supply passage and second chamber, with substantialelimination of air introduction into the second chamber occurring bycompletely submerging the input port in the drive fluid within the drivefluid reservoir when the input port is open to the drive fluid reservoirat all orientations of the diaphragm pump apparatus relative to theground.
 14. The method of clain 13, wherein step c further comprisesregulating the pressure within the second chamber through a valve influid communication with the second chamber.